[xj] ignition/starting problem

XJ
1

I have a 1987 XJ6 which I have owned for nearly ten years.
Begining about three months ago, I started to experience some
starting problems. The engine would crank over rapidly, but it
wouldn’t fire at all; sometimes, which I let the key return to
the ‘‘run’’ position, it would suddenly fire (sometimes not). In
examining the wiring diagram, I saw that 1980-on Jags had a hot
lead from the ignition to the coil, then on to the distributor.
The negative coil lead went to the distributor and to the ECU and
the tach. This basically reflects my wiring. However, my car has an
external ballast resistor with a connection to the coil and two
push connectors, one of which receives the white wire from the
ignition; the other connector is unused. I eventually discovered
that, when the car refused fire (sometimes it will start normally),
if I ran a jumper wire from the positive battery terminal to the
unused terminal on the ballast resistor, the car would fire. The
terminal on the starter relay that old diagrams show giving 12v to
the ballast when cranking is unused with no evidence of a wire ever
having been there…at any rate, it’s been that way for many years
without this problem.

So…questions: why do I have an external ballast resistor? Am I
supposed to have a coil with an internal resistor? What’s causing
this (the switch wire is always hot in run and cranking, HT lead to
coil is OK, connections tight, cap clean)? I thought of just
replacing the resistor, but I can find no listing (Moss, XK’s
Unlimited) for a ballast resistor for this year and model.

Any help would be much appreciated.

Bob–
robert manbeck
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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2

Bob, the ballast isn’t needed at all with the electronic ignitions in
these cars, so just toss it. The coil should see: a) two white wires
to its + terminal, b) two blk/wht wires to its - terminal, and c) one
wire with a blue spiral to its - terminal (that’s the tach wire). The
white wire from the harness is powered by the ignition key. The other
is power to the ignition amplifier down below.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

robert manbeck wrote:
[clip]

So…questions: why do I have an external ballast resistor? Am I
supposed to have a coil with an internal resistor? What’s causing
this (the switch wire is always hot in run and cranking, HT lead to
coil is OK, connections tight, cap clean)? I thought of just
replacing the resistor, but I can find no listing (Moss, XK’s
Unlimited) for a ballast resistor for this year and model.

===================================================
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3

In reply to a message from robert manbeck sent Thu 19 Mar 2009:

A test lamp or voltmeter on the coil positive would probably show
what the problem is. I would suspect the ignition switch is
possibly at fault and needs opening up for a bit of TLC. It sounds
like the ignition supply contacts are not making when the switch is
turned to the crank position. Or possibly there is a high
resistance (bad connection) on the ignition supply, and your jump
wire to the resistor is mimicking the original intention of the
circuit.
The general consensus is that the ballast resistor is not needed
on the CE ignition system, it would appear that someone has already
bypassed the resistor.
Maybe an easy fix would be to run a cable from the starter relay
C3 terminal to the coil +ve, although if the switch is starting to
play up that may give merely a temporary reprieve.

Dave–
The original message included these comments:

Begining about three months ago, I started to experience some
starting problems. The engine would crank over rapidly, but it
wouldn’t fire at all; sometimes, which I let the key return to
the ‘‘run’’ position, it would suddenly fire (sometimes not). In

–
Dave Collishaw '79 S2 Daimler Sov '92 xj40
Peterborough, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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4

In reply to a message from sparx sent Thu 19 Mar 2009:

The ignition switch is a very common fail area on these cars

Alex P–
alex paterson
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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5

Here’s something on cleaning the switch…

http://www.jag-lovers.org/snaps/snap_view.php3?id=1055809062

The main light switch may also come to need similar.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

sparx wrote:

In reply to a message from robert manbeck sent Thu 19 Mar 2009:

A test lamp or voltmeter on the coil positive would probably show
what the problem is. I would suspect the ignition switch is
possibly at fault and needs opening up for a bit of TLC. It sounds
like the ignition supply contacts are not making when the switch is
turned to the crank position. Or possibly there is a high
resistance (bad connection) on the ignition supply, and your jump
wire to the resistor is mimicking the original intention of the
circuit.
The general consensus is that the ballast resistor is not needed
on the CE ignition system, it would appear that someone has already
bypassed the resistor.
Maybe an easy fix would be to run a cable from the starter relay
C3 terminal to the coil +ve, although if the switch is starting to
play up that may give merely a temporary reprieve.

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

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6

robert manbeck wrote:

I have a 1987 XJ6 which I have owned for nearly ten years.
Begining about three months ago, I started to experience some
starting problems. The engine would crank over rapidly, but it
wouldn’t fire at all; sometimes, which I let the key return to
the ‘‘run’’ position, it would suddenly fire (sometimes not).

This is typical for a ign key problem, Robert - turned to ‘crank’ there
is no power to the coil etc. When the key is released the engine may
catch on the overrun as power is restored with the key to ‘run’…

Simple check; connect a jumpwire from batt pos to coil pos - it bypasses
some ign key connections. If this faithfully starts the car the ign key
is the culprit…

…if not, and(!) in any case; remove the external coil resistor -
connecting the white ign key wire directly to the coil pos. The
external coil resistor is not required and going bad it will interfere
with ignition.

Incidentally; one wire from the coil neg does not, ex factory, go to the
distributor - it goes to an ignition amplifier mounted at the front of
the engine. The other coil neg goes as you describe…

If neither of these ‘quickies’ restores normal starting; report back -
there are plenty of fish in this particular sea of sumptoms…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)> In

examining the wiring diagram, I saw that 1980-on Jags had a hot
lead from the ignition to the coil, then on to the distributor.
The negative coil lead went to the distributor and to the ECU and
the tach. This basically reflects my wiring. However, my car has an
external ballast resistor with a connection to the coil and two
push connectors, one of which receives the white wire from the
ignition; the other connector is unused. I eventually discovered
that, when the car refused fire (sometimes it will start normally),
if I ran a jumper wire from the positive battery terminal to the
unused terminal on the ballast resistor, the car would fire. The
terminal on the starter relay that old diagrams show giving 12v to
the ballast when cranking is unused with no evidence of a wire ever
having been there…at any rate, it’s been that way for many years
without this problem.

So…questions: why do I have an external ballast resistor? Am I
supposed to have a coil with an internal resistor? What’s causing
this (the switch wire is always hot in run and cranking, HT lead to
coil is OK, connections tight, cap clean)? I thought of just
replacing the resistor, but I can find no listing (Moss, XK’s
Unlimited) for a ballast resistor for this year and model.

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

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